The rivets may have a steel center pin, that was used to pull/ set the large pop rivet. Use a small steel pin punch the same diameter to punch it out. Then carefully drill out the aluminum hollow rivet.
I work in aviation so opted to use grade 5 short stainless machine screw and stainless nyloks. When I did the passenger door 3 mos ago.
Replace window motor and regulator as unit. There is spring inside the regulator strong enough chop off a finger or two. Disassembly not advised. The price isn't that much more , not worth the time and effort to change just one part.
Both parts have had a good service life. Replacing as a unit is easier and will operate like new. All metal edges are razor sharp use caution.
Good luck.